Data bus protocols such as the Consumer Electronics Bus, or CEBus, can be utilized for interconnecting consumer electronics devices such as television receivers, display devices, video-cassette recorders (VCR), and direct broadcast satellite (DBS) receivers. A bus protocol such as the CEBUS provides for communicating both control information and data. CEBus control information is communicated on a “control channel” having a protocol defined in Electronics Industries Association (EIA) specification IS-60. Control information for a particular application can be defined using a form of programming language known as CAL (Common Application Language).
Consumer electronics devices are becoming increasingly complex and provide an ever-increasing number of features. While coupling these complex devices together via a data bus may be necessary to provide a complete audio-video (A/V) system, doing so creates numerous problems. For example, certain features of one device may require interaction with one or more devices coupled to the bus. A capability of one device may be needed to complete a particular operation in another device. Conflicts between the needs of various devices may arise.
A specific example of an A/V system involving complex electronic devices coupled via a data bus is a system that includes a digital VHS format (DVHS) VCR, such as that being developed by Thomson Consumer Electronics, Inc., of Indianapolis, Ind., and a DSS® satellite receiver, manufactured by Thomson Consumer Electronics, Inc. The DVHS VCR can record either analog or digital signals. Various checks must occur before a recording can occur. For example, is the proper type of tape (analog or digital) loaded in the VCR? Is the user entitled to record a particular program: is the copyright status such that recording is permitted and has the user paid any fees required? Is the DSS® unit available to tune the desired program at the time a recording is to be made? Is the DSS® unit tuning the desired channel? In addition, a user must be informed, e.g., using on-screen display (OSD) messages, regarding the status of each device and what operations each device is performing. The complexity of each device and of the interactions involved creates a need for a robust system and method for communicating information between interconnected electronics devices.